2.  The cosmological constant that enters the definition (REF )
is not the one which is responsible for the observed accelerated
expansion of the Universe. The observable density of the cosmological
constant \(\rho _\Lambda ^{obs}=\Lambda /(8\pi G)\)  is a sum of the vacuum quantity \(\rho _\Lambda ^{vac}=\rho _\Lambda ^{vac}\)  and the induced density
\(\rho _\Lambda ^{ind}\)  coming from, e.g., the electroweak phase transition.
Both summands are many orders of magnitude greater than the observed
quantity \(\rho _\Lambda ^{obs}\) . For this reason, the numerical value of
\(\gamma _0\)  may be small, but it is not that small as some reader might
think. This issue was discussed in detail in [1]}, with the
consideration based on the unique effective action formalism
[2]}, [3]}, [4]}. This interesting approach is discussed
in a separate Chapter of this Section and does not fit the present review.
However, we shall briefly discuss the differences between the two
universal equations for \(\gamma (\mu )\)  below.
